Comment 5 for bug 1665310

I do not know what's wrong in your environment. But could u check [0], in 2.12.3, it load username rather than admin-user.
and in newton branch, other project is using username pattern, which works.

[0] https://github.com/openstack/keystoneauth/blob/2.12.3/keystoneauth1/loading/_plugins/identity/v3.py#L23